John Ramsay Show full post »
Bunkerbarge
Just as an observation offered for comment or input, from someone returning to the hobby after around 40-50 years of absence I do get the feeling that, as a hobby, it looks like nowadays we try to chase theoretical perfection and tend to loose sight of the fact that the basics, to me anyway, are generally far more important.  

Obviously using the example above, purely as an example, I really believe that counting the number of twists in a bus cable is a bit irrelevant when we then connect all the cables up with cable connectors that rely on a contact point which is less than the cross sectional area of the cable.  I've been convinced all my working life as a marine engineer that attending to and putting your efforts into achieving the best possible basics will lead to a large proportion of the theoretical perfection as unnecessary.  

From what I have learned so far about a DCC layout I see the BUS as the foundation for everything.  To me it should be as sound and as well fitted as possible but then I hear many examples of corners being cut as much as possible as regards the numbers of droppers used and the ways in which the droppers are connected really surprise me.  Selling fishplates with droppers soldered to them just baffles me!

I would like to see more of an emphasis on getting the basics right and putting time and effort into sound, solid best practises.  I personally would advocate soldering all droppers and I would also advocate droppers on every piece of track.  Many I accept would see that as unnecessary and over the top but I tend to think that is far better use of time than counting twists in the cable.

It would be interesting to see what other members views are, from both a new and a more established perspective.
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AHJAY
Disagree away by all means. I do not discuss things I have not seen and confirmed.

Yes, it will stop cross-talk in even analog installations, and is also effective for this in digital low power situations (in a different but similar way). I even have a reference somewhere about the phone cables on the S&C being replaced by twisted wire back in the 1930's to help with "phantom voices on the line".

However that does not change the fact that induction ALSO greatly increases the effective resistance in the circuit. The result is reduced power delivery. I have seen, measured and looked at the results on many larger layouts with a scope many times. It is a very real issue.

The layout of power wiring matters everwhere there is a waveform involved... from DCC to welding machines to high power Audio. All of the effects are real with real world consequences.

it is certainly NOT just academic for DCC / model railways. DCC is a slightly assymetric square wave that is affected FAR more than a simple sine wave situation when power use grows within the wire. While a small layout need not generally worry, if it becomes "busy" electronically then it too may suffer. If it is a medium to large layout, then twisting really matters.

BB - Its a simple thing and "Just do it" is the best advice. That is also why we sell pre-twisted wire, so modellers do not have to worry about doing it. I have seen MANY layouts that needed help because of poor wiring practice. ALL were fixed by improving things that did not, on the surface, look important.

We try hard to NOT go into the theory too much as modellers do not need to know - bit FYI, the 12 turns per metre is very much a measurable thing / result. It corresponds to cancelling induction at appx 8khz which is about the centre of the higher power range of DCC use. A tighter twist will affect higher frequencies, a less frequent one lower frequencies.

The actual maths is a good A4 page of Algebra with wiggly bits in the equations - you really do NOT want to go there LOL.


Regards, Ahjay
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Iain Morrison wimorrison
The twisted pair was actually invented by Alexander Graham Bell in 1881 😉

https://www.electronicsweekly.com/blogs/electro-ramblings/industry-comment/only-connect-twisted-pair-cabling-2013-07/

Iain Morrison
Modelling h0e using Z21 with iTrain automation and Railcom
There are also unknown unknowns – the ones we don't know we don't know
http://www.wimorrison.co.uk
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AHJAY
We should not forget just how much Scotland and the rest of the UK have created then given the world...

I was in the USA a while ago... Having dinner with an American who said "Nothing of value was ever really invented outside the USA for the last 100 years of more".

It took VERY great restraint for me to not plant my steak knife in him somwhere painful... then explain to him as he bled just how much Edison stole from others + what valuable technology they were gifted by the UK to secure support via lend-lease in WW2.

Ahjay
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Mister Rusty
''valuable technology they were gifted by the UK to secure support via lend-lease in WW2.''

Not the least of which was RDF [radar] and the Miles M52 supersonic research aircraft,
https://en.wikipedia.org/wiki/Miles_M.52
incorporating flap-reversal nullification, before they sorted out all the German technology stolen from Germany. They've spent millions re-inventing ww2 technology from many disparate sources and then shout loud the inference as to how clever ''their'' engineers are. Anything is forgivable if they want it bad enough.
One name?
von Braun.
Politics aside, brilliant team he developed.
Just watch out for the Paperclips 😉

Pete
Bunkerbarge,
I am locked out, hooked up on your last message, this is the only way that l can get into the forum.
Anyone else having issues?
Please check.
Could anyone reading  this, please advise Jazavalley or another admin , thanks
Be careful, in case it's a virus. The message received is:-
The last email that was sent to you was returned as spam by your email provider. Please update your account with a valid email address. Ahjay said  that my details are all in order, correct address and all.
Pete
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Bunkerbarge
I once had an American girlfriend so stayed in Texas a lot for a couple of years.  That is a fairly typical outlook of a great many Americans and, as my girlfriend was a teacher, I got a good number of opportunities to look at infant school textbooks.  Talk about creative writing!!
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